Mechanism for transmitting motion through a sealed wall



y 15, 1967 E. K. MACKENZIE 3,319,476

MECHANISM FOR TRANSMITTING MOTION THROUGH A SEALED WALL Filed July 8, 1965 6 Sheets-Sheet l 3' IN V EN TOR.

y 6, 1967 E. K. MACKENZIE 3,319,476

ECHANISM FOR TRANSMITTING MOTION THROUGH A SEALED WALL 6 Sheets-Sheet 2 Filed July 8, 1965 M Z .N M Wm WM mY m N m K m m 5 ATTORNEY-Y.

y 15, 1967 E. K. MACKENZIE 3,319,476

MECHANISM FOR TRANSMITTING MOTION THROUGH A SEALED WALL Filed July 8, 1965 6 Sheets-Sheet 5 fij--5 UPPER TRAVEL LIMIT L FEEDWATER PUMP-OFF LEVEL J-SWITCH L NORMAL WATER LEVEL L FEED WATER PUMP-ON LEVEL D'FFERENT'AL -L FUEL CUT-OFF LEVEL SWITCH FUEL CUT-OFF L6 LOWER TRAVEL LIMIT f DIFFERENTIAL INVENTOR. ELB ERT KENNEDY MACKENZIE May 16, 1967 E. K. MACKENZIE I 3,319,476

MECHANISM FOR TRANSMITTING MOTION THROUGH A SEALED WALL Filed July 8, 1965 6 Sheets-Sheet 4 g} INVENTOR.

y 16, 1967 E. K. MACKENZIE 3,319,476

MECHANISM FOR TRANSMITTING MOTION THROUGH A SEALED WALL Filed July 8, 1965 6 Sheets-Sheet 5 +13 y 1967 E. K. MACKENZIE MECHANISM FOR TRANSMITTING MOTION THROUGH A SEALED WALL Filed July 8, 1965 6 Sheets-Sheet 6 0 H HAH H IN VE N TOR. 25597 AF/V/VEDY MA (AfA/l/f United States Patent 3,319,476 MECHANISM FOR TRANSMITTING MOTION THROUGH A SEALED WALL Elbert Kennedy Mackenzie, Wales, Pat, assignor to Yarway Corporation, Philadelphia, Pa, a corporation of Pennsylvania Filed July 8, 1965, Ser. No. 470,542 3 Claims. (Cl. 74-18) The present invention relates to devices for transmitting motion through a sealed wall.

A purpose of the invention is to reduce the force required to transmit motion through a sealed wall to a minimum in order to achieve a low energy loss.

A further purpose is to reduce the force required in turning a shaft by reducing the energy absorption of the sealing device for the shaft.

A further purpose is to permanently secure a shaft at one end to a torsionally resilient shaft bearing and to rigidly mount this bearing at the other end, allowing the shaft to pass through a hermetically sealed wall.

A further purpose is to employ a polytetrafiuoroethylone or a similar plastic tube to surround and also pressure engage a torsion shaft and also by reason of its low coeflicient of friction to slip with respect to the shaft and thus to permit relative rotational motion of the tube and shaft with a minimum absorption of input energy.

A further purpose is to provide a motion transmitting device which is capable of operating at pressures of the order of several hundred psi. and at temperatures as high as the polyfluoroethylene plastic (or other material of the essential properties needed for a seal) will be capable of operating.

A further purpose is to facilitate operation at high temperatures because the coefficient of friction of the polytetrafluoroethylene or similar plastic against the shaft decreases with temperature.

A further purpose is to make a motion transmitting device which is insensitive to the pressure environment in which the motion to be transmitted originates.

A further purpose is to use a plastic tube surrounding the torsion shaft which is not wettable by most liquids, which has no tendency to adhere to the shaft and which is inert to water or most other fluids.

A further purpose is to load the plastic tube surrounding the torsion shaft in compression in such a way that even in the case of extensive damage to the sealed mechanism or sealed parts leakage will tend to be prevented by the pressure of the sealed environment acting to hold the tube tight against the shaft, thus making the device tend to fail safe.

A further purpose is to provide a motion transmitting device which will not be subject to failure by fatigue and which can be subjected to large degrees of overtravel without damage.

A further purpose is to provide a sealed motion transmitting device with the advantageous properties of a metal torque tube but capable of much greater angular rotation, much lower energy absorption and operating at a much lower stress value.

A further purpose is to provide a sealed motion transmitting device in which the input motion is transmitted through a sealed wall by means of a continuous rigid shaft with negligible friction and hysteresis losses.

A further purpose is to make a motiontransmitting device so sensitive that it will be applicable to float indicators operating on a buoyant force less than two grams and in condensate indicators for rotating process rolls.

A further purpose is to reduce the diameter of a float or displacer required in the level detecting device.

A further purpose is to provide a self-contained means of detecting liquid in horizontal rotating sealed drums Without any external source of power being required.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate a few only of the numerous embodiments in which the invention may appear selecting the forms shown from the standpoints of convenience in illustration, satisfactory operation and clear demonstration of the principles involved.

FIGURE 1 is a top plan view, partly in horizontal section, showing a device of the invention applied to a liquid level gauge and indicator.

FIGURE 2 is a section on the line 2-2 of FIGURE 1.

FIGURE 3 is a section on the line 3-3 of FIGURE 2.

FIGURE 4 is a fragmentary enlarged axial section of the torsion shaft motion transmitting device of FIGURES 1 to 3.

FIGURE 5 is a fragmentary perspective of a modified switch operating device of the invention, seen from the end of the shaft which is outside the closed space.

FIGURE 6 is an enlarged fragmentary side elevation of the mounting discs, pins and switch operating levers as shown in FIGURE 5.

FIGURE 7 is a diagram showing various positions which the float may achieve in the device of the invention, the positions being related to the shaft.

FIGURE 8 is a diagrammatic fragmentary sectional side elevation of a portion of the shaft outside the closed space, illustrating the use of a thrust bearing.

FIGURE 9 is an enlarged fragment of FIGURE 8.

FIGURE 10 is a sectional side elevation of a condensate indicator for rotating process rolls utilizing the sealed motion transmitting device of this invention.

FIGURE 11 is an enlarged fragmentary view taken along the lines 11-11 of FIGURE 10, showing in section the motion trans-mitting mechanism.

FIGURE 12 is a view of the indicator with its cover of alternate opaque and transparent segments partially broken away to reveal alternate colored segments on the indicator disc.

FIGURE 13 is a sectional view taken substantially along the line 13-13 of FIGURE 11 showing the spring biased centering mechanism for the indicator disc.

FIGURE 14 is an enlarged fragmentary view of the motion transmitting mechanism shown in FIGURE 11 showing the relationship between the various components on the torsion shaft and the hub of the indicator wheel, the shaft having been disengaged from the hub to more clearly show the individual components.

FIGURE 15 is a fragmentary sectional View taken along the lines 1515 of FIGURE 14 omitting the sealing bearing on the torsion shaft.

FIGURE 16 is an enlarged cross sectional view showing the relationship between the torsion shaft, the indexing extensions of the hub of the indicator wheel and the vertical extensions of the sealing plug taken along the lines 16-16 of FIGURE 11.

FIGURE 17 is a cross sectional view taken along the line 1717 of FIGURE 14.

FIGURE 18 is an enlarged fragmentary view taken within the circle 18 of FIGURE 10 showing in greater detail the connection between the detector arm and the torsion shaft.

FIGURE 19 is a full view of the detector arm taken in the direction of lines 19-19 of FIGURE 18, the phantom lines showing the arm in deflected position.

Describing in illustration but not in limitation and referring to the drawings:

A number of devices exist for transmitting motion through a sealed wall from a closed space such as a boiler or tank to the outside or vice versa. See, for example, Kinderman, U.S. Patent 3,067,623; Bosch, U.S.

Patent 2,607 ,233; Jones, US. Patent 2,877,994; and Miller, US. Patent 2,784,597.

One of the problems which has not yet been satisfactorily solved is the transmission ofmotion at moderate pressures, suitably up to 250 p.s.i. (steam at 405 F.) for long times or suitably up to 3000 p.s.i. at room temperature for shorter times, without substantial frictional drag which would reduce the sensitivity of the device.

The device of the present invention ofiers a very desirable solution of this problem. When applied to a liquid level gauge it is capable of operating on less than 0.006 inch of change in liquid level position. When applied to a rotating pressurized drum, it is capable of indicating minor amounts of liquid, usually stearn condensate, accumulating within the drum.

For short times it has successfully operated under 700 p.s.i. static steam pressure, and it has successfully withstood extended operation at 250 p.s.i. static steam pressure. Also static tests of 3000 p.s.i. have been made with success, exposing the device to the pressure for short times and using a thrust bearing as later described.

The device of the invention is so resistant to fatigue failure that it is possible on actual test to function without failure for as much as 1,000,000 shaft cycles.

One of the great advantages of the device of the invention is that the torsion shaft turns in contact with a surrounding tube of an organic plastic such as polyfluoroethylene which is constantly pressed into engagement with the torsion shaft. If the tube were of a material such as rubber which would tend to grip the shaft and apply high drag, this effect would greatly reduce the sensitivity. Because of the low coeflicient of friction, however, of the polyfluoroethylene, the shaft is free to slip with respect to the plastic tube, so that very little energy loss occurs. High angular deflection capability is possible with this device so long as it does not turn continuously in one direction and high overload and overtravel capacity are also possible.

By reason of its resistance to corrosion, the plastic tube is not likely to fail from corrosion or from encrustation of deposits, since 'most materials do not wet or corrode or adhere to it.

Unlike diaphra gms and bellows, in case extensive damage to the sealed mechanism or parts occurs, the device itself tends to seal against leakage, and catastrophic escape of pressure is not possible.

The device can be applied for operating electric switches, for manipulating valves, for manipulating indicators, and ultimately for performing many various control and indicating functions.

Thus the device can be used to advantage in liquid level indicators for boilers and tanks, for flow indicators, temperature indicators, condensate indicators, flow control devices, temperature control devices and level control devices or other devices.

In the drawings two applications of the motion transmission devices have been depicted but the invention does not thereby intend to be bound by these particular embodiments, as the device may equally be used within the scope of this invention in any control or indicating device or devices wherein a similar function is desired. In FIGURES 1-9 I have shown the sealed torsion shaft motion transmitting device as applied to a liquid level gauge. In FIGURES -19 I have shown the sealed torsion shaft motion transmitting device as applied to a condensate indicator.

Considering FIGURES 1-9 in detail, in the embodiment shown a liquid level gauge 20, communicating, for example, with the interior of a boiler, has a housing 21 exposed interiorly to boiler pressure and exteriorly suitably under atmospheric pressure.

A float 22 of any well known type is supported on a float arm 23 and floats at a suitable level on a liquid 24, which in one embodiment will be the water in a boiler, to indicate the water level. The housing is suitably sepa- 4 rable and gasketed at 21', held together with bolts not shown.

On a line corresponding to the axis of the end of the arm 23, a well 25 in the housing 21 provides a shoulder 26 at the outer end and engaged in the shoulder is a bearing 27 of a motion transmitting device 29 to be described. The -bearing 27 is sealed by a threaded gland nut 28 threaded into a packing opening 30 at the outside of the housing.

The motion transmitting device comprises a suitable metallic torsion shaft 31 which is conveniently straight from end to end as best seen in FIGURE 4 and which passes through and is in slip fit engagement with the inside of an opening 32 in the bearing 27 and is a free fit with the inside of an opening 33 in the gland nut 28.

At its inner end the torsion shaft mounts the float arm 23, as by providing a shaft cap 34 surrounding the inner end of the torsion shaft 31 and extending a pin 35 through an opening transversely through the shaft cap and the shaft as shown in is desirably bifurcated at 36 so that it extends on both sides of the shaft cap 34 at a reverse bend portion 37 of the arm 23, and is held in place by threading the pin at 38 through the float arm at 40. The bifurcated portion of the float arm engages a head 41 of the shaft cap 34 and the pin 35 extends diagonally so that it can be assembled in only one angular relationship of arm 23 and shaft 31.

In the preferred embodiment the bearing 27 will be made of stainless steel. Where, however, it is desired, another bearing material may be used for the bearing 27, such as bronze, or other corrosion resistant steel of adequate hardness.

The bearing 27 has a reduced end extension 42 fitting closely around the torsion shaft and at the outer end this extension is tapered at 43 so as to allow the plastic tube to conform to the shaft without great stress concentration at this point.

Surrounding the torsion shaft and in close conformity with it is a highly resilient or elastic plastic tube 44. The tube 44 will preferably be of polytetrafluoroethylene (Teflon) or of a similar polyfluoro (including polyfluorochloro) ethylene (Kel-F).

The plastic tube 44 surrounds and engages a reduced portion 42 of the bearing at one end as shown at 45, and then reduces in diameter under the pressure at 46 conformed to a tapered portion 43, and then extends around and in close conformity with the shaft at 47 until it is adjacent the opposite end of the shaft. Conveniently, a well 43 is provided inside the shaft cap for the end of the plastic tube 44.

The plastic tube is held tightly in engagement with the bearing 27 at one end and with the torsion shaft 31 at the other end 'by any suitable means. While wire wrapping may be used, I prefer to hold the engagements by helical spring 50 around the plastic tube at the opposite ends, the springs 50 being initially wound of smaller diameter and resiliently gripping the plastic tube. This spring gripping feature is in itself no part of my invention.

The operating disc 54 has suitably mounted at an adjustable but fixed position thereon an operating dog 55 suitably coated with a low friction material which extends into operative position with respect to one of a pair of operating levers 56 and 57 of snap acting switches 58 and 60.

Suitable connections are made to a terminal block 61.

FIGURES 5 and 6 show an improved mechanism for operating two snap acting switches at selective positions of the level sensing float travel. The disc assembly 54 mounted on the shaft 31 outside the closed space consists of an arm 61 permanently secured to the shaft and mounting in fixed angular relation to the shaft three operating pins, 62 projecting from a disc 63, 64 projecting fro-m a disc 65, and 66 projecting from a disc 67. All of the FIGURE 4. The float arm discs are concentric and have central openings which pass the shaft. The discs are secured to the arm 61 by a set screw 68 passing through aligned slots 70 in each of the discs. In order to permit adjustability of pin 64 it passes through a slot 71 in the outermost disc 63. In order to permit adjustability of the pin 66, it passes through aligned slots 72 in discs 63 and 65.

The switches 53 and 6h have projecting operating levers 56 and 57. The operating lever 57 is provided with a suitable counterweight 73.

Pin 62 projects under operating lever 56 of snap switch 58. Internal spring bias in the switch 58 continually urges switch operating lever 56 downward, away from the switch body and against pin 62. Clockwise rotation of the disc assembly 54 causes pin 62 to rise and when the switch lever 56 of switch 58 reaches the operating point, the switch snaps to the operated position as well known in prior art snap switches. Counterclockwise rotation of the disc assembly 54- causes pin 62 to lower, and when the operating lever 56 returns through the switch operating point, the switch snaps back to its normal free position.

Pin 64 extends above operating lever 57 of snap switch 60 and functions to move switch at to the operated position when rotation of disc 54 counterclockwise lowers pin 64 sufficiently. Counterbalance weight 73 attached to operating lever '7 partly offsets the internal spring bias tending to move switch operating lever 57 upward. Weight 73 is sufficient to keep the internal spring bias from returning switch 611 to its normal free position once it has snapped to the operated position. This weight, however, is not heavy enough to snap the switch to the operated position without assistance from some external downward force. Once the switch is operated by pin 64, switch 66 remains in this position until return to the normal free position by pin 66 exerting an upward force on switch operating lever 57 as the disc 54 rotates clockw1se.

The advantage of having adjustment of the operating pins on the disc will be evident from FIGURE 7. In FIGURE 7 float 22 when at the top is at a position L-l for the upper travel limit. The next lower position of the float L-2 corresponds to the level at which the feed water pump should be turned off and thus corresponds to the position at which switch 60 should cut off. The mid-position L-3 corresponds to the normal water level. The next lower float position L4 corresponds to the position at which the feed water pump should be turned on by switch 60, so that the distance between L-Z and L-4 represents the pump differential.

The next lower position L5 is the level at which fuel should be cut off from the boiler, by operation of switch 58. The lowermost position L6 is the lower travel limit so that the fuel cutoff differential is between L-4 and L-6.

In some cases it is important to provide a thrust bearing at the outer end of the shaft 31. As shown in FIG- URES 8 and 9, a bracket 74 extends across the end of the shaft, clearing from the operating pins in disc 54 or slotted to allow them to move freely. The bracket 74 has a bearing recess 75 in which the pointed end 76 of the shaft 31 is received to provide a pin and socket type thrust hearing. The end of the shaft desirably has a smooth rounded conical point.

The thrust bearing absorbs axial thrust from internal pressure on the opposite end of the shaft and permits operation at higher pressures at least up to 3000 psi.

In operation of the device, when the water level raises or lower the float, it moves the float arm 23 in a way to rotate the torsion shaft 31. The torsion shaft then turns and as it does so the plastic tube rotates and torsionally deflects at one end with respect to the other end. At the same time the plastic tube is urged by the pressure tightly against the torsion shaft. Because, however, of the low coefficient of friction of the torsion shaft with respect to the plastic tube, and especially at elevated temperatures where a steam installation is involved, the plastic tube does not take up the twist in the short length, under which conditions the drag on the motion transmitting device would be very great, but slips with respect to the torsion shaft to extend the relative motion along the length of the plastic tube, only the inner end of the plastic tube remaining angularly fixed with respect to the torsion shaft.

It will be evident that the shaft and tube need not be straight but can if desired be longitudinally curved.

Considering FIGURES 10 through 19 in detail, there is shown a liquid phase detector or condensate indicator utilizing the sealed novel motion transmitting device of this invention, wherein the indicator senses the presence of condensate or other liquids within a rotating and pressurized process roll or drum. These indicators are more fully described and claimed in another US. application of Charles Robert Bardes and James W. Williams, entitled Liquid Phase Detectors or Condensate Indicators Ser. No. 467,208 filed on June 28, 1965.

Briefly these devices provide, to an operator of a machine, a visual indication on the outside of the roll of the presence of condensate fluid within the roll. These indicators function independent of the direction of rotation or velocity of the roll and independent of the pressures existing inside the roll. In paper making equipment, where it is necessary to maintain constant temperatures in dryer rolls heated with steam, it is important to provide an indicating device which will show to the operator that the steam condensate is being properly drawn off, as an accumulation of condensate within the drum would vary adversely the temperatures of the roll.

The condensate indicator depicted here includes a sensing element or vane 81 adjacent the inner surface $2 of a process roll 80, which element will respond to the presence of liquid within the roll. A suitable visual indicating means 83 is located outside of and near the periphery of the drum revealing to an operator the actuation of the vane 81 by liquid in the drum through the sealed motion transmitting device generally indicated as 84 to be hereafter described.

The sensing vane responds to the presence of liquid spread over the inside surface of the roll by the centrifugal forces of rotation. The vane operates on the differential velocity that exists between the roll and the condensate which may have accumulated within it. In operation, as the roll is rotating, a layer of condensate is spread over the inside surface by the centrifugal forces of rotation, the fluid building up in speed until it rotates at the same speed as the roll. However, as the liquid depth increases as inner surface, the velocity of the liquid will tend to fall below the velocity of the roll as the centrifugal forces will not be sufficient to keep it at the same speed. Thus a differential in the speed of rotation of the indicator attached to the roll and the liquid layer at the point of response will be created. If, however, the differential velocity approaches zero there will not be any response from the vane because the liquid condensate would then be rotating at the same speed as the drum. Nevertheless, the vane functions when (1) the roll is not revolving fast enough to This invention provides a mechanism for transmitting the motion of this vane or sensing element in response to liquid msrde the pressurized drum through a sealed wall with a minimum of energy absorption by the sealing device without a loss of pressure to a suitable indicator means comprising a disc having reflective and nonreflective positions located outside of the drum, the visibility of the reflective portions indicating the presence of liquid within the drum. The detector unit is mounted in the end of a drum 80 which rotates in a horizontal plane at a point where the detector arm 85 assumes a radial position with the end of the vane or paddle 81 normally about one inch from the inner cylindrical drum surface.

As mentioned above, if the paddle strikes liquid as it passes through the bottom sector of a revolution while the drum is rotating at relatively slow speeds, a drag on the paddle will be created causing shaft 86 of the transmission means to rotate, thus rotating an indicating disc 87 divided suitably into twelve equal and alternating red and black segments. In a non-actuated position the red segments on the disc are hidden behind the opaque segments 89' of a protective cover 88 thereby showing only the black color. In FIGURE 12 the cover 88 is shown partly broken away to show the red segments beneath the opaque portions. When actuated the red segments are exposed through the transparent segments 89 of the cover 88, the disc having been rotated by the shaft thus indicating the presence of fluid in the drum. The disc is rotated not only when the paddle strikes liquid in the bottom of a drum rotating at relatively slow speeds but also when a drag is created on the paddle by a differential in velocity between the fluid and the drum when the drum is rotating at relatively faster speeds.

The protective cover is held in place by a housing 90 having flanges 91 for securing it to the side of the drum with suitable machine screws 92. As shown in FIGURE 11, the housing includes an inner hub portion 93, having the coils of helical torsion spring 94 surrounding it. Spring 94 is deflected so that its extension arms 95 and 96 are crossed and exert a continuous thrust against centering pins 97 and 98. Pin 97 is affixed to housing 90 and pin 98 is connected to the rotatable indicating disc 87. When disc 87 is rotated, pin 98 moves out of radial alignment with pin 97 increasing the torque in spring 94. The torque in spring 94 exerts a continuous tendency to return disc 87 to the angular position in which pins 97 and 98 are in radial alignment which establishes an equilibrium position or non-actuated position to which disc 87 will always return if permitted. When the spring is in equilibrium position, only the black portions of the indicating disc are seen through the cover. This spring 94 eliminates false signals from gravity effects during slow speeds of rotation or when stopped.

Indicating disc 87 includes a driving shaft 100 rotating within a guiding shaft bushing 101 in the hub 93 of housing 90. The driving shaft 100 includes a flattened tube 102 attached thereto that is engaged by a flat tongue 103 on one end of the actuator shaft 86. An extension 99 of the hub 93 of housing 90 includes an indexing key surface 104 which engages flats 105 on vertical extensions 119 of the sealing bearing or plug 106 associated with the actuator shaft 86 (see FIGURES 1417). This engagement as best seen in FIGURE 16 is to insure the proper positioning of the housing 90 relative to the detector arm 85 and paddle 81.

A sleeve body 107 is screwed into a pipe threaded hole 109 in the side of the steam drum 80 providing access to the drums interior. The detector arm 85, shaft 86 and sealing bearing 106 are inserted through the sleeve and are free to rotate for proper positioning until the lock nut 108 is tightened within the sleeve 107. Tightening of the lock nut 108 fixes the detector arm 85 in the proper angular position relative to the center of the steam drum and provides a metal-to-metal seal between the sealing bearing 106 and the indicator sleeve body 107 at 110.

As aforementioned, the sealing bearing may suitably be a stainless steel or if desired may be of other suitable material such as bronze or any other corrosion resistant steel of adequate hardness.

In accordance with the objects of the invention, the actuating or torsion shaft 86 is in scalable relation with the sealing bearing 106 by means of resilient tube 111 suitably of Teflon or other material as described above in connection with the float level indicating device. One end of the tube is affixed to an extension 112 of the sealing plug 106 by helical spring clamp 113. It then reduces in diameter under pressure at 119 conforming to the tapered end portion of the extension 112 extending around and in close conformity with the shaft 86. See FIGURE 4 for greater clarification of this connection between the tube and the sealing plug. The other end of the resilient tube 111 is fixed to the actuator shaft 86, in the same manner by helical spring 114 thus forming a positive seal between the steam pressure inside the drum and the outside atmosphere. The torsionally resilient tube 111 thus provides a low energy absorbing sealing device which permits angular rotation of the actuator shaft 86. The slot 115, as shown in FIGURE 16 formed between the vertical extensions 119 of sealing plug 106 provides a rotational limit stop to the tongue 103 of the actuator shaft 86 which limits the angular rotation of the shaft and the indicator disc 87. A short length of Teflon tubing 116 provides a low friction bearing between the actuator shaft 86 and the sealing bearing 106.

The condensate indicator sleeve body 107 includes a cylindrical portion 120 extending through the hole 109 in the drum 80, to which is rigidly fixed a protective tube 121 which protects the shaft 86 and houses bushing 122 suitably of brass at its inner end which also includes a short piece of Teflon as a bearing 123 as shown in FIGURE 18. This serves as a thrust bearing and lateral support for the actuator shaft 86.

A spring mount 124 is attached the actuator shaft 86 and held in place by a pin 125. This pin supports a torsion spring 126 and bracket 127 which pivots about pin 128. The assembly is fabricated in this manner in order to permit insertion of the detector arm through the drum access hole 109. The detector arm return torsion spring 126 positions the detector arm such that its center line is perpendicular to the center line of the actuator shaft 86. Spring 126 is .assembled with initial torsional deflection with one arm of the spring 126 pressing against the inside surface of spring bracket 127. This urges bracket 127 into the position shown perpendicular to the shaft 86, in which position it stops, normally by engagement of the edges of the bracket 127 against an edge face of spring mount 124. When the detector arm 85 and assembly is to be inserted into hole 109 in the drum the spring bracke 127 is rotated against the force of the spring 126 to the position shown in phantom in FIGURE 18. After the spring assembly passes the inside edge of the drum the arm will swing back to the perpendicular position. Spring bracket 127 in addition provides a housing for a centering torsion spring 103 around pin 129 which centers the detector arm 85 in line with bracket 127. This centering is accomplished with coil spring arms 131 and 132, in the same manner as the centering of the indicating disc 87 by spring 94 is accomplished as previously described. Edges 133 of spring bracket 127 and elements 134 affixed to an extension bracket 135, which rotates about pin.129, serve the same function as pins 97 and 98 in the previously described centering action. The detector arm extension bracket 135 serves as a clamp which holds the spring of detector arm 85 firmly in place. The spring detector arm 85 is a resilient energy absorbing device which is used to transfer drag forces against the paddle 81 into angular rotation of the shaft 86. To do this the helical spring includes initial tension between turns which adds to its stiffness as a cantilever beam allowing greater energy transfer to the shaft 86 and increasing its natural freto the inner end of quency. A high natural frequency is necessary to avoid fatigue from resonant vibration and also spurious signals.

As the paddle 81 is drag ed through the liquid, the shaft 86 will rotate causing the indicator disc to rotate in response to the angular movement of arm 85. However, especially when the arm is caused to run through a relatively stationary pool of liquid at the bottom of the roll, an initial impact of great force will be exerted on the paddle. If the arm were rigid in relation to the shaft such as an impact might snap it off. Thu a spring arm is provided which will allow deflection of the vane to relieve an overload of drag forces in a manner similar to that shown in FIGURE 19 in phantom. The most adverse conditions would exist when the drum was half full of liquid and would be operating at maximum speed. In this case the deflectable detector arm spring 85 bends until the faces of the paddle 81 are tangent to the drum radius for minimum drag. Then, if required, detector arm torsion spring 130 also deflects permitting the detect-or arm assembly 85 to pivot further decreasing the effective moment arm applying torque to shaft 86 to a value which can be absorbed without fatiguing of the detector arm spring 85. As the drag on the paddle ceases the arms of the spring 130 will recenter the arm 85 to its initial position. The length of arm 85 can suitably be constructed so as to place paddle 81 as near the drums inside cylindrical surface as desired.

The extension bracket 135 can be bent at 137 in order to position the paddle at any angle to the shaft 86 or the inside surface of the drum as is desired. See FIGURE where various positions of the arm are shown in phantom.

In operation, when the water level in the drum reaches the edge of the paddle 81 and causes a drag thereon, torsion shaft 86 turns in a slight angular motion which in turn rotates indicator disc 87 exposing the red segments from behind the opaque portion of transparent cover 88, thus indicating to anyone looking at the side of the roll that liquid is accumulating within the drum. As the shaft 86 turns, the plastic tube rotates and torsionally deflects one end with respect to the other end, as its inner end is being urged by the pressure in spring 114 against the shaft 86 and its outer end is affixed to extension 112 of the sealing bearing 106 by spring 113. Because of the low coefiicient of friction between the shaft and the tube, the tube twists with the shaft for only a short distance before the inner end of the tube slips with respect to the shaft, the outer end remaining angularly fixed to the sealing bearing 106. Thus a sealed bearing is provided which creates little drag on the motion transmitting device but yet successfully hermetically seals the aperture through which the device operates. The motion transmission mechanism can then be used to provide a condensate indicator that is compact, easily installable in new or existing installations with relatively no rotating projections for maximum safety, while providing an effective sealing means for the pressurized contents of the drum.

While the device described utilizes a straight shaft and tube member, the same can be longitudinally curved if so desired.

In view of my invention and disclosure, variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such insofar as they fall within the reasonable spirit and scope of my claims.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a mechanism for use in connection with a sealed wall, a torsion shaft extending through an opening in the wall, bearing means surrounding and journalling the torsion shaft and forming part of the sealed wall, a polyfluoroethylene plastic tube surrounding the bearing means at one end and then surrounding the torsion shaft toward the other end, the bearing means having a tapered end inside the tube with which tapered end the tube is in contact, said tapered end reducing the stress concentration on the tube, said tube under pressure being in contact with the portion of the bearing means which it surrounds and with the portion of the torsion shaft which it surrounds beyond the bearing means, means for securing the tube at one end to the bearing means and means for securing the tube at the other end to the torsion shaft, an arm attached substantially perpendicularly to the axis of rotation of the torsion shaft, said arm comprising a helical spring wound with an initial tension between turns, a sensing element located on the arm remote from the shaft, said element upon activation creating angular movement of the arm and axial rotation of the shaft and indicator means operatively connected to the torsion shaft outside the sealed wall.

2. In combination, a switch erating said switch comprising a torsion shaft extending through an opening in a sealed wall, bearing means surrounding and journalling the torsion shaft and forming part of the sealed wall, a polyfluoroethylene plastic tube surrounding the bearing means at one end and then surrounding the torsion shaft toward the other end, said tube under pressure being in contact with the portion of the bearing means which it surrounds and with the portion of the torsion shaft beyond the bearing means which it surrounds, means for securing the tube at one end to the bearing means, means for securing the tube at the other end to the torsion shaft, in combination with separate adjustable disc means mounted on with it, first, second and third pins relatively adjustably mounted on the disc means, a first switch having a switch operating lever which is above the first pin and resiliently urged to engage it, a second switch having a switch op erating lever which is below the second pin and resiliently urged to engage it, the third pin being below the operating lever of the second switch and all of the pins being on the same side of the disc with respect to the shaft, whereby rotation of the disc means in one direction causes the first pin to rise and engage the operating lever of the first switch to operate the first switch and movement of the second pin its pressure on the operating and a mechanism for opdirection relieves the pressure of the first pin on the operating lever of the first switch to permit the first 3. In a device of claim 2, counterweight means acting downward on the operating lever of the second switch against its spring bias to restrict the effect of the spring bias in moving the operating lever of the second switch.

References Cited by the Examiner UNITED STATES PATENTS MILTON KAUFMAN, Primary Examiner. 

1. IN A MECHANISM FOR USE IN CONNECTION WITH A SEALED WALL, A TORSION SHAFT EXTENDING THROUGH AN OPENING IN THE WALL, BEARING MEANS SURROUNDING AND JOURNALLING THE TORSION SHAFT AND FORMING PART OF THE SEALED WALL, A POLYFLUOROETHYLENE PLASTIC TUBE SURROUNDING THE BEARING MEANS AT ONE END AND THEN SURROUNDING THE TORSION SHAFT TOWARD THE OTHER END, THE BEARING MEANS HAVING A TAPERED END INSIDE THE TUBE WITH WHICH TAPERED END THE TUBE IS IN CONTACT, SAID TAPERES END REDUCING THE STRESS CONCENTRATION ON THE TUBE, SAID TUBE UNDER PRESSURE BEING IN CONTACT WITH THE PORTION OF THE BEARING MEANS WHICH IT SURROUNDS AND WITH THE PORTION OF THE TORSION SHAFT WHICH IT SURROUNDS BEYOND THE BEARING MEANS, MEANS FOR SECURING THE TUBE AT ONE END TO THE BEARING MEANS AND MEANS FOR SECURING THE TUBE AT THE OTHER END TO THE TORSION SHAFT, AN ARM ATTACHED SUBSTANTIALLY PERPENDICULARLY TO THE AXIS OF ROTATION OF THE TORSION SHAFT, SAID ARM COMPRISING A HELICAL SPRING WOUND WITH AN INITIAL TENSION BETWEEN TURNS, A SENSING ELEMENT LOCATED ON THE ARM REMOTE FROM THE SHAFT, SAID ELEMENT UPON ACTIVATION CREATING ANGULAR MOVEMENT OF THE ARM AND AXIAL ROTATION OF THE SHAFT AND INDICATOR MEANS OPERATIVELY CONNECTED TO THE TORSION SHAFT OUTSIDE THE SEALED WALL. 